Process of making alloys



Patented July 25, 1933 UNITED STATES PATENT OFFICE DONALD W. RANDOLPH, OF FLINT, MICHIGAN, ASSIGNOR TO A C SPARK PLUG COM- PANY, OF FLINT, MICHIGAN, A COMPANY OF MICHIGAN PROCESS OF MAKING ALLOYS N0 Drawing.

This is a continuation in part of my prior application S. N. 520,704, filed March 6, 1931.

This invention relates to a process of making alloys containing low melting point metals such as barium. Barium has a low work functionin other words, it gives off electrons easily,so that alloys containing it are particularly desirable for use in spark plug electrodes to give a low and uniform sparking voltage, and in the cathodes of vacuum tubes and the like because of the profuse emission of electrons with small current con sumption.

Owing to the fact that barium has a low melting point and is readily oxidized con siderable difiiculty has been experienced in the past in alloying it with suitable base metals. By following my method it is possible to produce at will alloys containing any desired barium content within the limits disclosed. I have chosen nickel as the base metal for the reason that it alloys well with barium and possesses in itself properties valuable for use in spark plug and vacuum tube electrodes. The closely related metal, cobalt, also possesses some advantages as a base for the alloy as will be pointed out.

In preparing the alloy, nickel is melted, preferably in a high frequency induction furnace, although this is not essential. The melt is preferably held at a temperature a little above the melting point, and to the melt is preferably added a proportion of manganese, for example, 2 parts of manganese to 98 parts of nickel. The manganese performs its usual functions as a deoxidiz'er. The temperature of the melt is then preferably raised from a little above the melting point, which is about 2620 F. to approximately 2800 F. to 2850 F. and is held at that temperature for from 2 to 5 minutes to insure thorough alloying of the elements. I prefer the shorter period. Next 0f 1% magnesium is added, this addition being for the purpose of rendering the alloy more ductile. The melt is then held at the same temperature for one minute, to insure thorough admixture of the magnesium with the other constituents.

The barium furnished in blocks or bars and I have foundfit essential to protect it Application filed May 26,1932. Serial No. 613,767.

nickel wire about the package and plunging it beneath the surface of the molten metal, using the wire as a handle. The barium is added in amount equalling about 2% of the melt, and is added one minute after the addition of the magnesium. After the addition of the barium, the melt is permitted to stand for about 30 seconds and is then poured into a warm steel mold. 250 F. is a suitable mold temperature.

By adhering to the steps outlined I am able to consistently produce alloys containing as high as .17 barium. I have also found that the time schedule is equally satisfactory for 2 lb. melts and for 250 lb. melts, although it might be thought that a longer alloying time would be necessary with the larger amount of metal.

I regard as the most important step of the method, the maintaining of the temperature of the metal somewhat above the melting point, for example, in the neighborhood of 2800 F. to 2850 F. and casting of the ingot within a very short period, i. e. thirty seconds, after the addition of the barium. If the melt were allowed to stand for many minutes after the addition of the barium practically none of the barium would be found to be present in the cast ingot.

In the larger melts I have found it desirable to add the barium in lumps not exceeding 100 grams each, adding two or more of the lumps to produce the desired constituency.

place of nickel. Cobalt seems to increase thermionic emission. I have made by the described methods alloys differing from that detailed, by the substitution of cobalt for 80% of the nickel. I have found, however,

that the addition of more than 25% cobalt produces an alloy that corrodes rapidly when used as a spark plu electrode. I have used the term nickel-co altmetal to designate this preferred group of base metals.

I have also made an alloy of this type by first making a sub-alloy of 45% nickel and 55% manganese, this composition having the lowest bo1ling point of any combination of nickel and manganese. To this sub-alloy I have added bar1um, and the resulting alloy I have added to nickel to form the esired composition, but this modification has produced no better results than the preferred procedure.

I have found it desirable in some cases to add chromium to the alloy. In the case of spark plug electrodes the addition of chromium reduces corrosion, and for this purpose from 1 to 20% may be added. An alloy ofthis type containing chromium has also proven of special value for vacuum tube filaments. I have described and claimed in m arch 6, 1931, a nickel-barium-chromium alloy suitable for these purposes.

The chromium is preferably added to the alloy before the barium, the procedure belng otherwise that given above.

I claim:

1. The method .of producing an alloy of nickel and barium which consists in melting the nickel metal and maintaining it at a temperature of approximately 2800 F. to 2850 coating or covering the barium to render itim IVlQllS to air and molsture, Immersing t e barium'beneath the surface of the melt, and maintaining it at the said temperature for a short period to insure thorough alloying, and immediately pouring the resulting alloy.

2. The method of producing an alloy of nickel and barium which consists in melting the nickel and maintaining it at a temperature of approximately 2800 F. to 2850 F., coating or covering the barium to render it its immersion in the melt, immersing the barium beneath the surface of the melt and maintaining it at the said temperature for a short time, on the order of 30 seconds, to insure thorough alloying, and immediately pouring the resulting alloy.

3. The method of producing an allo of nickel and barium which consists in melting the nickel, adding suitable amounts of a deoxidizing agent, maintaining the melt at a temperature of approximately 2800 F., coating or covering a quantity of barium to render it impervious to air and moisture and to temporarily protect it from the heat of the melt to permit of its immersion therein, inserting the barium thus prepared beneath the surface of the melt and maintaining it at such temperature for a short time, on the order of thirty seconds, to insure thorough alloying, and immediately pouring the resulting alloy into a suitable mold.

4. The method of producing an alloy of nickel and barium, which consists in melting the nickel and. maintaining it at a temperature of approximately 2800 F. to 2850 F., providing a quantity of barium with a consumable coating to exclude air and moisture, and with an outside fusible metallic coverin inserting the barium thus pre ared beneat the surface of the melt and mamtaining it at such a temperature for a short time to insure thorough alloying, and immediately pouring the alloy into a suitable mold.

5. The method of producing an alloy of nickel and barium which consists in melting the nickel metal, maintainin it at a temperature but slightly above m lting, adding a small percentage of a suitable deoxidizing y agent raising the temperature to approxico ending application Serial No. 520,703 filed mately 2800 F. to 2850 F. and holding it there for a few minutes to insure thorough alloying, adding a small proportion of magnesium to render the alloy ductile, holding the melt at said temperature for approximately one minute, coating or covering a quantity of barium to render it impervious to air and moisture and to temporarily protect it from the heat of the melt to permit of its immersion therein, inserting the barium thus prepared beneath the surface of the melt and maintaining it at said temperature for a short time, on the order of thirty seconds, to insure thorough alloying, and immediately pourin the alloy.

6. T e method of producing an alloy of nickel and barium, which consists in melting the nickel, maintaining it at a temperature but slightly above melting, adding a small percentage ofmanganese, raising the temperature to approximately 2800 F. to 2850 F. and holding it there for from two to five minutes to insure thorough alloying, adding impervious to air and moisture and permit a small proportion of magnesium to render the alloy ductile, holding the melt at said temperature for approximately one minute, providing a quantity of barium with a consumable coating to exclude air and moisture, and with a fusible-metal covering, inserting the barium thus prepared beneath the'surface of the melt and maintaining it at said temperature for a short time, on the order of thirty seconds, to insure thorough alloying and immediately ourin the alloy.

DON RANDOLPH. 

